Zynga began rolling out Facebook Credits on some of its games months ago. But now they’ve made Facebook Credits the primary payment solution on all of their games across the Facebook platform other than Poker and a few other smaller games. Users can wire transfer cash, or use Facebook Credits, but that’s it. Other third party payment providers have been removed.

The migration has clearly had bumps – a slew of Zynga users are screaming murder in the forums over various payments failures. Which makes sense since Zynga is almost certainly accounting for the lion’s share of the Facebook Credits business.

One thing to note – Don’t expect to see Facebook Credits being rolled out in Zynga’s games on other platforms like Yahoo. Zynga and Facebook have found détente for now, but I don’t see Zynga processing a single dollar through Facebook that they don’t have to.

Zynga and Facebook’s joint statement: “Facebook and Zynga have transitioned Facebook Credits to be the exclusive method of payment for most Zynga network games on the Facebook platform. The companies are committed to working together to provide the best possible customer experience during this transition.”

Update: To clarify, Poker and the rest of Zynga’s games on the Facebook platform will eventually use FB credits, too.